The present invention relates to integrated circuit devices, and in particular high voltage transistors, power MOSFETs, IGBTs, thyristors, MCTs, diode, and the like (“power devices”).
A power device is a device that is capable of handling currents in excess of 1 A and/or handles 50 volts or more. Some power devices are configured to handle 10 kA or more and/or 4 kV. Generally, power devices handle few hundred volts or more. The power device may be two terminal devices, e.g., diodes, or three terminal devices, e.g., transistors. In the three terminal devices, the control terminals (e.g., base or gate) determines the characteristics of the conduction path between the two other terminals or conduction terminals. These terminals are the emitter and collector in the bipolar transistor, and the source and drain in the field-effect transistor, and the anode and cathode in the thryristors. The control function can be exercised either by the injection of current or through the voltage of the control electrode. If the injection of current is used the control electrode makes a direct contact with the semiconductor substrate. If the voltage of the control electrode is used, the control electrode is separated from the substrate by a dielectric layer to prevent current flow between the control electrode and the substrate.
The power devices are rated according to their blocking voltage capability. Generally, there are two types of blocking voltages: forward blocking voltage and reverse blocking voltage. Regardless of the types of the power devices, there is a great interest in providing a power device that has an improved forward blocking voltage or reverse blocking voltage, or both since such a device would tend to be more robust and could be used in wider applications.